Microscopical Society of Victoria. 
81 
envelope which followed tlie contact of the igneous mass, without 
regard to the angular position of the sedimentary beds it affected. 
I have invariably found these effects to lessen gradually in pro¬ 
ceeding from any place of greatest metamorphic change, until the 
formations assume the characteristic appearance of our Silurian 
series. Finally, veins and dykes are found to pass from the 
intrusive masses into the broken contact edges of the sediments. 
It is therefore evident, that the great masses of granites and 
diorites are younger than and apparently intrusive into the Silurian 
formations. 
The granitic rocks of the locality I am describing form one of 
those intrusive masses of which I have spoken, and the dykes, 
which are the subject of these notes, pass through the granite, but 
not so far as I have observed through the surrounding sediments. 
The suspicion arises, therefore, that they may be of the same 
formation and age as the containing granitic rocks which con¬ 
tain them. 
These dykes are all in the neighbourhood of Mount Budgee 
Budgee. I have observed that they are usually double, that is, 
there are generally two dykes running parallel and at but little 
distance apart. They principally occur near Granite and Bulgo- 
back Creeks, and it is in this order that I shall take them. 
Granite Creek Dyke .—The dyke at this place is single, and first 
shows on the summit of Pretty Boy’s Pinch in proceeding north¬ 
ward along the track near the contact of the granite and the 
sediments. Where it first shows, it is probably not more than 
twenty-four inches in width, running on a strike of N. 10° W. 
It continues to show itself in places along the track for about ten 
chains as subangular grey masses. On examining a fresh fracture, 
the dyke stone is found to have a dark grey or bluish compact 
ground mass, showing porpliyritic crystals of greyish white trans¬ 
lucent felspar, and some plates of shining black mica. The mica 
can be distinguished as forming rhombic crystals. 
A very short distance further on, at the crossing of Granite 
Creek, the dyke turns to N. 75° W., and crosses the course of the 
stream. It is here about fifteen feet in width. It weathers in 
rough angular masses of a grey colour. In the weathered surfaces 
I have distinguished two felspars. The most frequent are in long, 
rather translucent, bluish grey prisms, the other in dull white 
F 2 
